Here we go again! I received a call just today, regarding the old California Vehicle Code 27150. This law is a regulation written to control noise pollution. The current standard is a maximum of 95db.

All this is just fine and dandy, but how is it enforced? Our understanding is a law enforcement agent can write a ticket for excessive noise at his or her discretion. Back in 1958 an officer could actually go into a parking lot and write tickets for any vehicle that had glasspacks. That vehicle did not necessarily have to be running, nor would the owner be present. In the early 60's we fought and won a ruling that not all glasspacks were illegal. This first act is what brought about SEMA.

The only time I remember any officer using a decimeter was when they ran noise abatement teams in the Highway Patrol. Their testing was not done by the standards set by the Society of Automotive Engineers. There were tickets written for loud exhaust in a crowded freeway. Many more noises were being picked up on their meters, besides the vehicle they were pinpointing. The shops that had installed those exhaust systems were required to replace the aftermarket mufflers at no charge. That program did not last more than a couple years, but put the hurt on several small Mom and Pop shops.

 On the side of our law enforcement, there are many vehicles on the road that should be pulled over and ticketed for loud exhaust. If you are one of those vehicle owners, and you are ticketed you will have to make an appointment with your local referee, after you have repaired or replaced the exhaust.

Just so you California vehicle owners know, the law also states that you can be written a ticket for any exhaust manifold leak, exhaust pipe leak, muffler leak or tailpipe leak. You can also be written a ticket for holes in your floorboards or firewall. This law, if enforced helps the vehicle owner, because if you ignore any of these problems, you can cause your own health problems, due to all the carbon monoxide entering into your vehicle.

For the concerned shop owner, I would recommend purchasing a well know brand of decimeter. Not the cheapest thing known to man! Something with a range of up to 130db- learn how to use it.

Now, how to run an exhaust sound test with you new meter:

Locate a noise testing area. The area that you select should be over 25 ft. away from any wall or building to avoid reflective sound (echo) and vehicle should be on flat ground. Have the vehicle running and at operating temperature. Place the decimeter at a 45° angle from the exhaust outlet and 20 inches away from that outlet. Microphone should be at same height as the outlet.

Set the Decibel Meter: Set the meter in the “A” setting, for ear frequencies. Set the decibel range for the legal limit. You can set the timing for either fast or slow for metering the exhaust sound.

Rev the engine: Press the accelerator to rev the engine to 50 to 75% of the maximum safe rpm limit. Most official tests use the 50% test.

Take the reading: read the meter and record your reading. There are about 10db allowances for wind and ambient noise. Document on your invoice what you read.

I mention this last point for any concerned shop owner, who has just installed an aftermarket system on a vehicle. Knowing that he vehicle will pass the decimeter test, and documenting it may just save you a future headache and a few dollars. You will also know that on future vehicles of the same year, make, model and engine, you can feel confident to install the same exhaust.

Hopefully, this has been some “sound” advice from an old mufflerman!